1. Field of the Invention
This invention relates to a BGA (Ball Grid Array) type semiconductor device which has a plurality of ball-shaped conductive terminals.
2. Description of the Related Art
A CSP (Chip Size Package) receives attention in recent years as a three-dimensional mounting technology as well as a new packaging technology. The CSP means a small package having about the same outside dimensions as those of a semiconductor die packaged in it.
A BGA type semiconductor device has been known as a type of CSP. A plurality of ball-shaped conductive terminals made of metal such as solder is arrayed in a grid pattern on one principal surface of the BGA type semiconductor device and is electrically connected with the semiconductor die mounted on the other side of the package.
When the BGA type semiconductor device is mounted into electronic equipment, the semiconductor die and external circuit on a printed circuit board are electrically connected by compression bonding of each of the conductive terminals to each of wiring patterns on the printed circuit board.
Such a BGA type semiconductor device has advantages in providing a large number of conductive terminals and in reducing size over other CSP type semiconductor devices such as an SOP (Small Outline Package) and a QFP (Quad Flat Package), which have lead pins protruding from their sides. The BGA type semiconductor device is used, for example, as an image sensor chip for a digital camera incorporated into a mobile telephone.
FIGS. 30A and 30B show outline structure of a conventional BGA type semiconductor device. FIG. 30A is an oblique perspective figure of a front side of the BGA type semiconductor device. And FIG. 30B is an oblique perspective figure of a back side of the BGA type semiconductor device.
A semiconductor die 104 is sealed between a first glass substrate 102 and a second glass substrate 103 through epoxy resins 105a and 105b in the BGA type semiconductor device 101. A plurality of ball-shaped terminals 106 is arrayed in a grid pattern on a principal surface of the second glass substrate 103, that is, on the back surface of the BGA type semiconductor device 101. The conductive terminals 106 are connected to the semiconductor die 104 through a plurality of second wirings 110. Each of the plurality of second wirings 110 is connected with each of aluminum wirings pulled out from inside of the semiconductor die 104, making each of the ball-shaped terminals 106 electrically connected with the semiconductor die 104.
More detailed explanation on a cross-sectional structure of the BGA type semiconductor device 101 will be given referring to FIG. 31. FIG. 31 shows a cross-sectional view of the BGA type semiconductor devices 101 divided along dicing lines into individual dice.
A first wiring 107 is provided on an insulation film 108 on a surface of the semiconductor die 104. The semiconductor die 104 is bonded to the first glass substrate 102 with the resin 105a. A back surface of the semiconductor die 104 is bonded to the second glass substrate 103 with the resin 105b. 
And one end of the first wiring 107 is connected to the second wiring 110. The second wiring 110 extends from the end of the first wiring 107 to a surface of the second glass substrate 103. And the ball-shaped conductive terminal 106 is formed on the second wiring 110 extended onto the second glass substrate 103.
However, there is a possibility that the first wiring 107 and the second wiring 110 are disconnected at a point of contact between them, since the area of the point of contact is very small. Also there is a problem in step coverage of the first wiring 107.